Porous intervertebral distraction spacers

ABSTRACT

An intervertebral space distraction and implantable device assembly provides sequentially axially wider spacers that are to be sequentially inserted into and removed from an intervertebral space to widen the space until a desired anatomical spacing of the adjacent vertebral bones is restored. The set of spacers includes a porous spacer that is as wide as the spacer that restores the desired anatomical spacing. The porous spacer can therefore be left implanted in the intervertebral space to promote fusion of the adjacent vertebral bones.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/906,123, filed Jul. 16, 2001, entitled “PorousIntervertebral Distraction Spacers”.

FIELD OF THE INVENTION

[0002] This invention relates generally to a treatment for scoliosis andmore specifically to the instruments, implants, distracting trialspacers, and surgical methodology used in the treatment and correctionof scoliosis.

BACKGROUND OF THE INVENTION

[0003] The bones and connective tissue of an adult human spinal columnconsists of more than 20 discrete bones. These more than 20 bones areanatomically categorized as being members of one of fourclassifications: cervical, thoracic, lumbar, or sacral. They are coupledsequentially to one another by tri-joint complexes that consist of ananterior intervertebral disc and the two posterior facet joints. Theanterior intervertebral discs of adjacent bones are cushioning cartilagespacers.

[0004] The spinal column of bones is highly complex in that it includesthese 20 bones coupled to one another (and others), and it houses andprotects critical elements of the nervous system having innumerableperipheral nerves and circulatory bodies in close proximity. In spite ofthese complications, the spine is a highly flexible structure, capableof a high degree of curvature and twist in nearly every direction.

[0005] Genetic, congenital and/or developmental irregularities are theprinciple causes that can result in spinal pathologies in which thenatural curvature of the spine lost. Scoliosis is a very common one ofthese types of irregularities, resulting in a sequential misalignment ofthe bones and intervertebral discs of the spine. Major causes ofscoliosis are idiopathic (i.e., unknown cause), congenital developmentalanomalies and neuromuscular disorders such as cerebral palsy. Themisalignment usually manifests itself in an asymmetry of the vertebralbodies, such that, over a sequence of spinal bones, the spine twistsand/or bends to one side. In severe cases, neurological impairmentand/or physiological disability may result.

[0006] The present surgical technique for treating scoliosis (as well asother spinal conditions) includes the implantation of a plurality ofhooks and/or screws into the spinal bones, connecting rods to theseelements, physically bracing the bones into the desired positions, andpermitting the bones to fuse across the entire assembly. Thisimmobilization often requires anterior plates, rods and screws andposterior rods, hooks and/or screws. Alternatively, spacer elements arepositioned between the sequential bones, which spacers are oftendesigned to permit fusion of the bone into the matrix of the spacer fromeither end, hastening the necessary rigidity of the developing bonestructure. Spacers allow bone fusion to grow into or around them. Thereare two classes of intervertebral spacers: horizontal cages such as theBAKTM and Ray cages, as described and set forth in exemplary U.S. Pat.No. 5,015,247 to Michelson and U.S. Pat. No. 5,026,373 to Ray et al.,respectively, and vertical cages such the Harms cages, as described andset forth in exemplary U.S. Pat. No. 4,820,305.

[0007] Similar techniques have been employed in other spinalinfirmities, including collapsed disc spaces (failure of theintervertebral disc), traumatic fractures, and other degenerativedisorders. While the present invention has many applications, suchapplications include the treatment of any spinal disorder in which thespace between vertebral bones needs to be surgically separated (thebones distracted), realigned and then fused to one another.

[0008] A variety of systems have been disclosed in the art which achieveimmobilization and/or fusion of adjacent bones by implanting artificialassemblies in or on the spinal column. The region of the back that needsto be immobilized, as well as the individual variations in anatomy,determine the appropriate surgical protocol and implantation assembly.With respect to the failure of the intervertebral disc, and theinsertion of implants and/or height restorative devices, several methodsand devices have been disclosed in the prior art.

[0009] Restoring the appropriate height and orientation of the vertebralbones and the intervertebral space is the first step in the surgicalstrategy for correcting this condition. Once this is achieved, one classof surgical implantation procedures involves positioning a device intothe intervening space. This may be done through a posterior approach, alateral approach, or an anterior approach. Various implant devices forthis purpose include femoral ring allograft, cylindrical metallicdevices (i.e., cages), and metal mesh structures that may be filled withsuitable bone graft materials. Some of these implant devices are onlysuitable for one direction of approach to the spine. All of thesedevices, however, are provided with the intention that the adjacentbones will, once restored to their appropriate alignment and separation,then grow together across the space and fuse together (or at least fuseinto the device implanted between the bones).

[0010] Most recently, the development of non-fusion implant devices,which purport to permit continued natural movement in the tri-jointcomplex have provided great promise. The instrumentation and methods forthe implantation of these non-fusion devices, as well as theimplantation of the fusion devices catalogued previously, thereforeshould integrate the functions of restoring proper anatomical spacingand easy insertion of the selected device into the formed volume.

[0011] It is, therefore, an object of the present invention to provide anew and novel treatment for scoliosis, as well as for the treatment ofspinal pathologies in general.

[0012] It is, correspondingly, another object of the present inventionto provide an intervertebral distraction trial tool which moreaccurately and easily separates collapsed intervertebral spaces.

[0013] It is further an object of the present invention to provide anintervertebral distraction trial tool which more can be used to correctscoliosis and/or restore normal alignment to the spine.

[0014] It is further an object of the present invention to provide aninstrument that proficiently and simply manages the insertion, rotation,and removal of the intervertebral distraction trial tools.

[0015] It is further an object of the present invention to provide animplantable spacer device that permits more anatomically appropriate andrapidly osteogenic fusion across the intervertebral space.

[0016] Other objects of the present invention not explicitly stated willbe set forth and will be more clearly understood in conjunction with thedescriptions of the preferred embodiments disclosed hereafter.

SUMMARY OF THE INVENTION

[0017] The present invention is directed to a method of treatment ofscoliosis and other spinal disorders. This method of treatment furtherincludes several new and novel instruments, implantable trialdistraction elements, and intervertebral spacer implants. Inasmuch asthe description of the new and novel method cannot be complete without adescription of each of these integral members, the following includesample explanation of these elements as well as description of thesurgical techniques.

[0018] First, the patient spine is exposed through an anterior approach(i.e., the surgeon creates an access hole which permits directinteraction with the anterior and/or anterio-lateral portion of theintervertebral bodies). In the case of scoliosis, as well as in otherdisorders in which the intervertebral space requires distraction and/orrepositioning, the surgeon removes the intervertebral disc material,usually leaving some portion of the annulus (the cylindrical weave offibrous tissue which normally surrounds and constrains the softercartilage cushion of the disc material). The surgeon then, insuccession, inserts a series of intervertebral trial spacers of definedwidth. Each of the series of spacers is of a progressively widerthickness, resulting in the continual widening of the space untilrestoration of the proper disc height has been achieved. Proper discheight restoration is determined by surgical experience, and byobservation of the annulus. (Often, the tightening of the annulusindicates that the proper disc height has been reached, inasmuch as theannulus is much less likely to be distorted by the same disruption thatcaused the intervertebral disc to collapse in the first place.)

[0019] More particularly, with respect to the specific instrumentsdisclosed herein, a series of solid trial spacer elements and aninstrument for their insertion and removal is now provided. Each trialspacer is a generally cylindrical disc having a deep annular groove atits midpoint, which forms a central trunk and radial flanges at each endof the trunk. Stated alternatively, two cylindrical upper and lowerhalves of the disc are held in a closely coaxial spaced apartassociation by the central trunk, which forms a coaxial bridge betweenthe upper and lower halves. The annular groove is particularly usefulfor holding the spacer using the spacer insertion instrument of theinvention, described below, in that the holding end of the insertioninstrument fits within the groove.

[0020] A variety of features of embodiments of the trial spacer elementsare disclosed. In some embodiments, such as the first and secondembodiments described below, support portions (the portions that are incontact with the adjacent vertebral bodies when the spacer is disposedbetween the bodies) of the top and bottom surfaces are parallel. Spacershaving this feature are generally described herein as “constantthickness” trial spacers. In other embodiments, such as the third andfourth embodiments described below, the support portions are notparallel, providing an overall taper to the spacer at an angle. Spacershaving this feature are generally described herein as “taperedthickness” trial spacers. The tapered thickness trial spacers areparticularly useful for treating scoliosis, as described below.

[0021] Other features of embodiments of the trial spacer elementsinclude beveled flanges and non-parallel annular groove walls. Morespecifically, in some embodiments, such as the second and fourthembodiments described below, the flanges are radially beveled in that anouter edge of the top surface of the disc is tapered toward an outeredge of the bottom surface of the disc. In other embodiments, such asthe first and third embodiments described below, the flanges are notradially beveled in this manner. The radial beveling feature can beparticularly useful for easing the insertion of the spacer in betweencollapsed vertebral bodies, as described below. Further, in someembodiments, such as the first and third embodiments described below,the walls of the annular groove are parallel, such that the floor of thegroove is as wide as the opening of the groove. In other embodiments,such as the second and fourth embodiments described below, the walls ofthe annular groove are tapered toward one another with the increasingdepth of the groove, such that the floor of the groove is narrower thanthe opening of the groove. Each type of annular groove is useful,depending on the particular surgical application and on the particularembodiment of the spacer insertion instrument that is used to insert thespacer.

[0022] Collections of trial spacer elements are provided by theinvention. Preferably, each spacer in a particular set maintains thesame diameter as the other spacers in the set. (It shall be understoodthat different collections of spacers may be provided such that thediameter of the selected collection of trial spacers is appropriate forthe specific patient being treated.) Also preferably, each spacer in aparticular set has a predetermined depth that differs from the depth ofthe other spacers in the set. The predetermined depth is provided inthat while each spacer in the set shares the same annular groovedimensions (so that each can be held by the same insertion instrument),each spacer has a different flange thickness (in sets where the spacersare constant thickness spacers). For sets of tapered thickness spacers,the predetermined maximum depth and predetermined minimum depth (the twodepths providing the overall taper) are provided in that while eachspacer in the set shares the same annular groove dimensions (so thateach can be held by the same insertion instrument), each spacer has adifferent maximum flange thickness and a different minimum flangethickness. Preferably in sets of tapered thickness spacers, the overalltaper angle is the same for each spacer in the set. The usefulness ofproviding sets of spacers similar in most respects except for the depthdimension will be described in greater detail below.

[0023] With regard to the instrument for the insertion and removal ofthe trial spacer elements, a first embodiment (particularly useful forinserting constant thickness trial spacers) of a spacer insertion toolincludes an elongated shaft and a handle at one end of the shaft. Thedistal end of the shaft includes semi-circular hook that is adapted tohold a trial spacer within an enclosure formed by the hook. The angleswept out by the hook is slightly greater than 180 degrees, but theinner diameter of the hook is only slightly larger than the centraltrunk of the trial spacer. Therefore, the trial spacer may be snappedinto the enclosure, but maintains complete rotational freedom within itsgrasp. A loading tool may be provided to assist in the loading andunloading of the trial spacer from the trial spacer insertion instrumentof this embodiment. This loading tool comprises a forked hook having twocurved tines separated by a notch that engages the shaft of theinsertion tool as the tines engage the flanges of the trial spacer, toforce the trial spacer into the enclosure. Alternatively and/oradditionally, the same device may be utilized to remove the spacer fromthe enclosure, by reversing the position of the forked hook relative tothe insertion tool and the spacer.

[0024] The insertion tool of this embodiment can be used to insert aseries of constant thickness trial spacers (some of which may havebeveled flange edges for easing the insertion between the collapsedbones and into the space to be distracted). More specifically, thinnertrial spacers can initially be inserted into the spacer, followedsuccessively by thicker trial spacers until the desired spacing isachieved. Once the appropriate spacing has been achieved, immobilizationof the spine by fixation, fusion, or non-fusion techniques and devices,such as those set forth in co-pending U.S. patent application Ser. Nos.09/906,117 and 09/906,118, entitled “An Intervertebral Spacer DeviceHaving a Wave Washer Force Restoring Element” and “An IntervertebralSpacer Device Having a Spiral Wave Washer Force Restoring Element”,respectively, as well as U.S. Pat. No. 5,989,291, entitled “AnIntervertebral Spacer Device”, each of which has been assigned to thesame assignee as this present invention, the specifications of which areall fully incorporated herein by reference, may be desirable.

[0025] While simple distraction to a constant height across theintervertebral space is appropriate for standard disc compressionpathologies, in the case of scoliosis, simple constant thicknessdistraction is insufficient to remediate the pathological condition.What is necessary is the distraction of the sequence of spaces, each toan appropriate angle and height, such that the overall spinalconfiguration is anatomically correct. Tapered trial spacers, such asthose disclosed in the present application, are the first suchdistraction tools to provide such a tailored correction of themisangulation of the spinal bones.

[0026] More particularly, the surgeon inserts the tapered trial spacersinto the intervertebral space (presumably from the anterior, oranterio-lateral, approach) with the narrow edge of the trial spacerforming a wedge and sliding between the adjacent bones. By utilizingeither a second or third embodiment of the spacer insertion tool,described more fully below, the surgeon may turn the spacer around itsaxis within the intervertebral space to find the most appropriaterotational position (corresponding to the most desirable straighteningeffect on the spinal column). Stated alternatively, each of the taperedtrial spacers has an overall wedge shape that generally corresponds tothe pathological tapering of the adjacent bones that characterizesscoliosis. By rotating the wedge-shaped spacer after it has been placedbetween the adjacent bones, the overall disc alignment may becompensated, restoring appropriate anatomical status. It should beunderstood that additional rotation of the spacer may restore lordosisto the spine, and that over-rotation (if the particular spine isflexible enough) of the spacer would result in a pathological curvaturein the opposite direction.

[0027] This second embodiment of the spacer insertion tool includes ahandle and an elongated dual shaft, the dual shaft culminating in atrial spacer grasping pincer, rather than the simple hook of the firstembodiment. This pincer differs from the hook of the first embodiment ofthe trial spacer insertion tool described above, inasmuch as the dualshaft includes a fixed shaft and a selectively engagable shaft which,together, form pincer. More specifically, the fixed shaft includes asemicircular hook portion of the pincer at its distal end, having anenclosure within which a trial spacer can be placed. The selectivelyengagable shaft includes the complementary portion of the pincer, whichmoves toward the hook portion to grasp and hold the trial spacer whenthe engagable shaft is engaged, and moves away from the hook portion torelease the trial spacer when the engagable shaft is disengaged. (Thespacer can be unloaded and loaded when the engagable shaft isdisengaged.) The engagement action prevents the spacer from movingrelative to the tool, and therefore permits the surgeon to rotate thetapered spacer in between the vertebral bodies (by contrast, the firstembodiment of the trial spacer insertion instrument permitted the spacerto rotate freely in the enclosure of the hook). There are alternativeinsertion and rotating instruments that may be designed, so long as theyselectively and alternatingly release or hold the trial spacer securelyagainst rotation (the spacer cannot be permitted to rotate freely if itmust be turned in the intervertebral space). The tapered trial spacersthemselves can include angle markers that clearly indicate to thesurgeon the amount of rotation that was necessary for the correction ofthe spinal deformity. Such angle markers can also serve as a guide forthe implantation of a secondary bone graft (e.g., a femoral ring) oranother intervertebral spacer device.

[0028] Once the surgeon has determined the appropriate geometry for thesurgical implants via the trial spacers, he or she is ready toimmobilize the spine in that position. While multiple ways forimmobilizing the spine are disclosed in the prior art, any one of whichand others may be suitable for the specific surgical patient'streatment, three alternative ways are herein described.

[0029] First, the trial spacers may be left in the patient while rodfixation apparatuses (anterior or posterior) are mounted to the spine,thereby holding the spine in its desired orientation even after thetrial spacers are subsequently removed. Alternatively, surface platingand/or intervertebral cage devices may be mounted to the spine topromote fusion without the need for bulky rod assemblies. (While thisapproach may seem more surgically desirable, questions regarding thelong term stability of these constructs have led some surgeons to chosecombinations of rodding and cages.)

[0030] A third approach to immobilizing the corrected spine is to inserta shaped bone graft, or suitably contoured porous metal spacer, into theproperly distracted intervertebral space, and either plating or usingrod fixation to hold the construct stable as the spine fuses. Theinsertion of a femoral ring allograft, or porous metal implant, into anintervertebral space is described more fully in co-pending U.S. patentapplication Ser. No. 09/844,904, entitled “A Porous Interbody FusionDevice Having Integrated Polyaxial Locking Interference Screws”,assigned to the same assignee as the present invention, thespecification of same being fully incorporated herein by reference.

[0031] The tapered trial spacers may also serve as precursors (measuringinstruments) for another spacer (e.g., a porous metal spacer), similarlyshaped, which is inserted into the intervertebral space by the sameinstrument.

[0032] Therefore, the present invention, in its many embodiments andcomponents, is directed to a surgical treatment for restoring a properanatomical spacing and alignment to vertebral bones of a scoliosispatient. In one desired embodiment, the present invention comprises asurgical method, which in a first embodiment, comprises: 1. determiningan angular misalignment associated with at least one pair of adjacentvertebral bones; 2. sequentially inserting and removing a series ofprogressively wider cylindrical spacer elements into the correspondingintervertebral space between said at least one pair of adjacentvertebral bones until the proper anatomical spacing between the pair ofadjacent vertebral bones is restored; 3. for each intervertebral space,inserting a diametrically tapered cylindrical spacer element into theintervertebral space between said corresponding pair of adjacentvertebral bones; and 4. rotating said diametrically tapered cylindricalspacer element such that the rotational orientation of the taperedcylindrical spacer element introduces the appropriate counter offset tothe intervertebral space of the previously misaligned scolioticvertebral bones, thereby restoring the proper anatomical alignment ofthe vertebral bones.

[0033] It shall be understood that each of said progressively widercylindrical spacer elements includes substantially parallel upper andlower surfaces. The method may also include the additional step ofaffixing immobilizing instrumentation to the vertebral bones of thepatient to hold the restored vertebral bones rigidly in position tofacilitate fusion, and positioning bone fusion material adjacent to therestored vertebral bones. It shall be understood that other equivalent(or alternatively efficacious) means for facilitating healing, such asincluding positioning a non-fusion intervertebral spacer device betweenthe restored vertebral bones so that a proper anatomical motion may bepossible.

[0034] The surgical treatment set forth above should be further refinedinasmuch with respect to the diametrically tapered cylindrical spacerelements, such that each has a width along its central cylindrical axissubstantially equivalent to the axial width of the final cylindricalspacer element utilized in the step of sequentially inserting andremoving the series of progressively wider cylindrical spacer elementsto restore the proper anatomical spacing between the pair of adjacentvertebral bones.

[0035] It shall be understood that each progressively wider cylindricalspacer element and/or diametrically tapered cylindrical spacer elementmay comprise solid or porous metal, or a porous or non-porous organicimplantable material.

[0036] For clarity, this embodiment of the surgical method includesexposing an intervertebral space between adjacent vertebral bones,distracting the space by sequentially inserting therein and subsequentlyremoving therefrom a plurality of intervertebral spacers, each having apre-determined thickness, the thicknesses incrementally increasing fromone spacer to another at an increment acceptable for safely distractingthe space to a desired distance, and when adjustment of an angularmisalignment of the adjacent vertebral bones is necessary, inserting,and when necessary rotating, in the intervertebral space, at least onediametrically tapered intervertebral spacer having a thickness along itscentral cylindrical axis sufficient to maintain the desired distancebetween the adjacent vertebral bones, and a diametrical angle sufficientto reorient the adjacent bones to the desired configuration, whenrotational adjustment of the angular misalignment is necessary, rotatingsaid tapered intervertebral spacer within the space until the desiredalignment is established.

[0037] In an alternative embodiment, in which porous spacers areutilized, the surgical method of the present invention may comprise:determining an angular misalignment associated with at least one pair ofadjacent vertebral bones; sequentially inserting and removing a seriesof progressively wider cylindrical spacer elements into thecorresponding intervertebral space between said at least one pair ofadjacent vertebral bones until the proper anatomical spacing between thepair of adjacent vertebral bones is restored; for each intervertebralspace, inserting a diametrically tapered cylindrical porous spacerelement into the intervertebral space between said corresponding pair ofadjacent vertebral bones; rotating said diametrically taperedcylindrical porous spacer element such that the rotational orientationof the tapered cylindrical porous spacer element introduces theappropriate counter offset to the intervertebral space of the previouslymisaligned scoliotic vertebral bones, thereby restoring the properanatomical alignment of the vertebral bones; and stabilizing the pair ofadjacent vertebral bones to permit infused growth of bone into thediametrically tapered cylindrical porous spacer element.

[0038] As shall be readily understood, in its most basic form, themethod of the present invention principally consists of sequentiallyinserting and removing a series of progressively wider cylindricalspacer elements into the intervertebral space between adjacent vertebralbones until the distance between the vertebral bones is anatomicallyappropriate.

[0039] More particularly, with respect to the various spacers of thepresent invention, in its most basic form, the spacers comprise aplurality of sequentially axially wider disc spacer elements, thesequential insertion and removal of which, into an intervertebral spaceeffects a widening of the intervertebral space, such that a desiredanatomical spacing of adjacent vertebral bones may be restored. Thesespacers may include beveled upper and lower circumferential radial edgeswhich facilitate the application of the desired spreading force to theadjacent vertebral bones. For the ease of surgical use, these spacersmay each include an engagement locus which couples with a correspondinginsertion and removal tool to facilitate the same. This locus comprisesan axially medial groove into which said insertion and removal tool canbe seated. In two alternative embodiments, the medial groove maycomprises a constant width, such that each disc spacer element mayrotate freely within the corresponding insertion and removal tool.Alternatively, the groove may be a radially widening groove, such thateach disc spacer element may be prevented from rotating freely withrespect to the corresponding insertion and removal tool by a clampingaction thereof, thereby permitting the controlled rotation of thecorresponding disc spacer element within the intervertebral space bymanipulation of the insertion and removal tool.

[0040] Tapered spacers, for use in reorienting as well as distractingthe alignment of the adjacent vertebral bones may be used. These taperedspacers comprise diametrically tapered upper and lower surfaces.Ideally, for surgeon measurement purposes, each of the disc spacerelements includes at least two relative angle designation marks on atleast one of said upper and lower surfaces such that a surgeon user mayreadily visually determine the rotational angle of said disc spacerelement relative to a known reference.

[0041] It shall be understood that the intervertebral spacers each havea unique axial thickness, the thicknesses increasing sequentially fromone spacer to another, the increasing thicknesses increasingincrementally, said plurality of spacers being particularly useful forgradually distracting adjacent vertebral bones in an anatomicallyappropriate manner.

[0042] A critical feature of the present invention is the potential forusing porous spacers to distract and potentially reorient the spine, andthat the spacers may be implanted permanently into the space between thevertebral bones such that bone ingrowth and solid fusion may occuracross the intervertebral space.

[0043] As introduced above, insertion tools are additional components ofthe present invention. In a first embodiment, the instrument forinserting and removing an intervertebral spacer into and out from anintervertebral space between adjacent vertebral bones, the spacer havinga trunk portion having a longitudinal axis and flange portions at eachlongitudinal end of the trunk, the instrument comprises: a shaft havinga proximal end and a distal end; said proximal end including a handle;and a holding structure provided at the distal end, which holdingstructure includes an enclosure within which the trunk of the spacer maybe selectively introduced and maintained therein, the holding structurehaving an opening leading to the enclosure and through which opening thetrunk of the spacer may be selectively passed to when forcedtherethough. More specifically, the trunk of the spacer has a firstwidth, the opening has a second width which is incrementally smallerthan the first width, and the enclosure has a third width whichaccommodates the first width, such that selective introduction of thetrunk through the opening and into the enclosure requires a force toelastically widen the opening such that the trunk may pass through theopening and into the enclosure, the restoration of the opening providingan occlusion which maintains the trunk within the enclosure. Assuggested above, the trunk is generally cylindrical and, therefore, theholding structure includes a hook having a curvate extent which forms apartial-circular enclosure, and which curvate extent fits between theflanges when the trunk is maintained within the enclosure.

[0044] In such an embodiment, the intervertebral spacer is selectivelysnapped into and out of the enclosure through the opening, and such thatthe intervertebral spacer may be rotationally freely held within theenclosure. In order to snap the spacer into and out of the enclosure, asecond element is often utilized. This second helper tool comprises ahandle portion at one end, and a bifurcated pair of spaced apart curvatehook-shaped tines at the other. The times have a radius of curvaturegreater than that of each of the spacers, such that when the first andsecond elements engage one another (at a fulcrum point at the point ofbifurcation of the spaced apart curvate hook-shaped tines and a pointbetween the handle and enclosure ends of the first element), theintroduction and removal of the distraction member from the enclosure isfacilitated.

[0045] In a second embodiment, which is more suited for the insertion,rotation and removal of the tapered spacers, the tool comprises a shafthaving a proximal end and a distal end, said proximal end forming ahandle and the distal end forming a spacer member engaging subassembly;said spacer member engaging subassembly including at least oneselectively expanding and contracting enclosure into which the centralcore may be introduced when the engaging subassembly is in the expandedstate, and which holds the spacer member so that it cannot move when theselectively expanding and contracting enclosure is rendered into thecontracted state; and an actuating mechanism, extending from theproximal end to the distal end, by which the spacer member engagingsubassembly may be selectively expanded and contracted. Morespecifically, the spacer member engaging subassembly comprises a fixedcurvate hook defining a portion of the enclosure, a second, selectivelyadvanceable and retractable, portion adjacent the fixed hook portion andsaid first and second portions forming said selectively expanding andcontracting enclosure. Stated alternatively, the selectively expandingand contracting enclosure is formed by at least two members which aremaintained in selectively slideable association with each other, atleast one of said at least two members including a tapered edge thereof.

[0046] The instrument of this embodiment includes an actuating mechanismincluding a trigger element disposed in the handle portion, whichtrigger is actionably coupled to advancing and retracting cams which arecoupled to the second portion to advance and retract the second portionin accordance with selective manipulation of the trigger. In moredetail, the spacer member engaging subassembly comprises a fixed memberand a selectively moveable member which, together, form said selectivelyexpanding and contracting enclosure, and wherein said actuatingmechanism comprises a trigger which is mechanically coupled to saidselectively moveable member, the mechanical coupling including a rod, aplate having a protrusion, and a lever having a slot, the rod beingconnected at one end to the selectively moveable member and at anotherend to the plate, the protrusion engaging the slot, the lever beingattached to the trigger, so that when the trigger is engaged, the leverpulls the plate protrusion by the slot, the plate pulls the rod, and therod moves the selectively moveable member toward the fixed member.

[0047] In a third embodiment, the tool comprises a shaft having aproximal end forming a handle, and a distal end forming a clawsubassembly for holding said spacer, said claw subassembly including afirst pincer which is fixed at the distal end of the shaft and a secondpincer which is selectively rotateable into and out of spacer holdingassociation with said first pincer to hold and release, respectively,the spacer; and an actuation mechanism for selectively rotating thesecond pincer. The second pincer is rotateably mounted to the shaft andis spring biased away from the first pincer.

[0048] In this embodiment the actuation mechanism comprises a slidingmember mounted to the shaft which is selectively moveable in the distaldirection by a force sufficient to overcome the bias of the spring, thedistally directed movement of the sliding member thereby causing thesecond pincer to move toward the fixed first pincer, and the subsequentretraction of the sliding member in a proximal direction causes thesliding member to disengage the second pincer and the permits thepincers to separate under the bias of the spring. In order to facilitatethis action, the second pincer includes a tapered surface which isengaged by a corresponding surface of the sliding member, saidengagement causes the second pincer to rotate relative to the firstpincer.

[0049] More specifically, the intervertebral spacer comprises acylindrical member having an annular groove defining a central axialcore portion and a pair of flange portions at opposing ends thereof; andthe claw subassembly engages the spacer at the central axial core.

[0050] Stated alternatively, this third embodiment comprises a pair ofpincers, a first of this pair being fixed, and a second being coupled tothe first in open-biased opposition thereto, and a sliding element whichmay be selectively translated into and out of engagement with saidsecond pincer to close and open the pair of pincers, respectively. Thepair of pincers define an intervertebral spacer grasping enclosurehaving an access opening through which the intervertebral spacer can bepassed for placement into the enclosure when the sliding element is outof engagement with the second pincer, and the spacer is securelymaintained between the first and second pincers when the sliding elementhas been translated into engagement with the second pincer. Ideally, thefirst and second pincers are mounted at the distal end of a commonshaft, and the sliding element is translateable along said shaft; andwherein the second pincer has a portion thereof which is engaged by thesliding element to close the pair of pincers. In addition, the secondpincer is mounted to the common shaft by a pivot joint, and the portionof the second pincer which is engaged by the sliding element is atapered surface, the angle of which tapered surface, when engaged by thesliding element, causes the second pincer to rotate about the pivotjoint, closing the first and second pincers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0051]FIGS. 1a-c illustrates a first embodiment of an intervertebraltrial spacer of the invention is illustrated in side, top and sidecutaway views, respectively.

[0052]FIG. 1d illustrates a first set of intervertebral spacers of theinvention in a side view.

[0053]FIGS. 2a-c illustrate a second embodiment of an intervertebralspacer of the invention in side, top and side cutaway views,respectively.

[0054]FIG. 2d illustrates a second set of intervertebral spacers of theinvention in a side view.

[0055]FIGS. 3a-c illustrate a third embodiment of an intervertebralspacer of the invention in side, top and side cutaway views,respectively.

[0056]FIG. 3d illustrates a third set of tapered intervertebral spacersof the invention in a side view.

[0057]FIGS. 4a-c illustrate a fourth embodiment of an intervertebralspacer of the invention in side, top and side cutaway views,respectively.

[0058]FIG. 4d illustrates a fourth set of tapered intervertebral spacersof the invention in a side view.

[0059]FIG. 5a illustrates a first embodiment of a spacer insertion tool500 of the invention in a side view.

[0060]FIG. 5b is a cutaway view of the insertion tool of FIG. 5a holdingthe spacer of FIGS. 1a-c.

[0061]FIG. 6a-b illustrates an embodiment of a loading accessory for aspacer insertion tool of the invention in side and top views,respectively.

[0062]FIG. 6c shows the loading accessory of FIGS. 6a-b in operation toload the spacer of FIG. 1a-c into the spacer insertion tool of FIG. 5a.

[0063]FIG. 6d shows the loading accessory of FIGS. 6a-b in operation tounload the spacer the spacer insertion tool of FIG. 5a.

[0064]FIG. 7a illustrates another embodiment of a spacer insertion toolof the invention in a side view.

[0065]FIG. 7b is a cutaway view of the insertion tool of FIG. 7a holdingthe spacer of FIGS. 4a-c.

[0066]FIGS. 8a-b illustrates yet another embodiment of a spacerinsertion tool of the invention in open and closed side views,respectively.

[0067]FIG. 8c is a cutaway view of the insertion tool of FIGS. 8a-bholding the spacer of FIGS. 4a-c.

DETAILED DESCRIPTION OF THE INVENTION

[0068] While the present invention will be described more fullyhereinafter with reference to the accompanying drawings, in whichparticular embodiments and methods of implantation are shown, it is tobe understood at the outset that persons skilled in the art may modifythe invention herein described while achieving the functions and resultsof this invention. Accordingly, the descriptions which follow are to beunderstood as illustrative and exemplary of specific structures, aspectsand features within the broad scope of the present invention and not aslimiting of such broad scope. Like numbers refer to similar features oflike elements throughout.

[0069] First, the patient spine is exposed through an anterior approach(i.e. the surgeon creates an access hole which permits directinteraction with the anterior and/or anterio-lateral portion of theintervertebral bodies). In the case of scoliosis, as well as in otherdisorders in which the intervertebral space requires distraction and/orrepositioning, the surgeon removes the intervertebral disc material,usually leaving some portion of the annulus (the cylindrical weave offibrous tissue which normally surrounds and constrains the softercartilage cushion of the disc material). The surgeon then, insuccession, inserts a series of intervertebral trial spacers of definedwidth. Each of the series of spacers is of a progressively widerthickness, resulting in the continual widening of the space untilrestoration of the proper disc height has been achieved. Proper discheight restoration is determined by surgical experience, and byobservation of the annulus. (Often, the tightening of the annulusindicates that the proper disc height has been reached, inasmuch as theannulus is much less likely to be distorted by the same disruption thatcaused the intervertebral disc to collapse in the first place.)

[0070] More particularly, with respect to the specific instrumentsdisclosed herein, a series of solid trial spacer elements and aninstrument for their insertion and removal is now provided. Each trialspacer is a generally cylindrical disc having a deep annular groove atits midpoint, which forms a central trunk and radial flanges at each endof the trunk. Stated alternatively, two cylindrical upper and lowerhalves of the disc are held in a closely coaxial spaced apartassociation by the central trunk, which forms a coaxial bridge betweenthe upper and lower halves. The annular groove is particularly usefulfor holding the spacer using the spacer insertion instrument of theinvention, described below, in that the holding end of the insertioninstrument fits within the groove.

[0071] A variety of features of embodiments of the trial spacer elementsare disclosed. In some embodiments, such as the first and secondembodiments described below, support portions (the portions that are incontact with the adjacent vertebral bodies when the spacer is disposedbetween the bodies) of the top and bottom surfaces are parallel. Spacershaving this feature are generally described herein as “constantthickness” trial spacers. In other embodiments, such as the third andfourth embodiments described below, the support portions are notparallel, providing an overall taper to the spacer at an angle. Spacershaving this feature are generally described herein as “taperedthickness” trial spacers. The tapered thickness trial spacers areparticularly useful for treating scoliosis, as described below.

[0072] Other features of embodiments of the trial spacer elementsinclude beveled flanges and non-parallel annular groove walls. Morespecifically, in some embodiments, such as the second and fourthembodiments described below, the flanges are radially beveled in that anouter edge of the top surface of the disc is tapered toward an outeredge of the bottom surface of the disc. In other embodiments, such asthe first and third embodiments described below, the flanges are notradially beveled in this manner. The radial beveling feature can beparticularly useful for easing the insertion of the spacer in betweencollapsed vertebral bodies, as described below. Further, in someembodiments, such as the first and third embodiments described below,the walls of the annular groove are parallel, such that the floor of thegroove is as wide as the opening of the groove. In other embodiments,such as the second and fourth embodiments described below, the walls ofthe annular groove are tapered toward one another with the increasingdepth of the groove, such that the floor of the groove is narrower thanthe opening of the groove. Each type of annular groove is useful,depending on the particular surgical application and on the particularembodiment of the spacer insertion instrument that is used to insert thespacer.

[0073] Collections of trial spacer elements are provided by theinvention. Preferably, each spacer in a particular set maintains thesame diameter as the other spacers in the set. (It shall be understoodthat different collections of spacers may be provided such that thediameter of the selected collection of trial spacers is appropriate forthe specific patient being treated. For example, the diameters of thetrial spacers in a collection that is suitable for use with pediatricpatients would be smaller than the diameters of the trial spacers in acollection that is suitable for use with adult patients.) Alsopreferably, each spacer in a particular set has a predetermined depththat differs from the depth of the other spacers in the set. Thepredetermined depth is provided in that while each spacer in the setshares the same annular groove dimensions (so that each can be held bythe same insertion instrument), each spacer has a different flangethickness (in sets where the spacers are constant thickness spacers).For sets of tapered thickness spacers, the predetermined maximum depthand predetermined minimum depth (the two depths providing the overalltaper) are provided in that while each spacer in the set shares the sameannular groove dimensions (so that each can be held by the sameinsertion instrument), each spacer has a different maximum flangethickness and a different minimum flange thickness. Preferably in setsof tapered thickness spacers, the overall taper angle is the same foreach spacer in the set. The usefulness of providing sets of spacerssimilar in most respects except for the depth dimension will bedescribed in greater detail below.

[0074] Referring now to FIGS. 1a-c, a first embodiment of anintervertebral trial spacer 100 of the invention is illustrated in side,top and side cutaway views, respectively. The spacer 100 is acylindrical disc with an annular groove 102 that forms a central trunk103 and radial flanges 104,106 at each end of the trunk 103. In thisembodiment, support portions 108,110 of the top and bottom surfaces112,114 of the disc are parallel. Further in this embodiment, the walls120,122 of the annular groove 102 are parallel, such that the floor 124of the groove 102 is as wide as the opening 126 of the groove 102.Further in this embodiment, the spacer 100 has a central bore 128.

[0075] Referring now to FIG. 1d, a set of intervertebral spacers 100 a-lof the invention are illustrated in a side view. Each spacer 100 a-l isformed generally similarly to the intervertebral spacer 100 of FIGS.1a-c, except that each spacer 100 a-l has a predetermined depth (denotedby the preferred dimension identified adjacent each spacer) provided inthat while each spacer 100 a-l shares the same annular groove dimensionsas the other spacers, each spacer 100 a-l has a different flangethickness dimension. For example, the flanges 1041,1061 are thicker thanthe flanges 104 a,106 a.

[0076] Referring now to FIGS. 2a-c, a second embodiment of anintervertebral spacer 200 of the invention is illustrated in side, topand side cutaway views, respectively. Similarly to the spacer 100, thespacer 200 is a cylindrical disc with an annular groove 202 that forms acentral trunk 203 and radial flanges 204,206 at each end of the trunk202. However, in this embodiment, the flanges 204,206 are radiallytapered in that support portions 208,210 of the top and bottom surfaces212,214 of the disc are parallel, while an outer edge 216 of the topsurface 212 is tapered toward an outer edge 218 of the bottom surface214. Further in this embodiment, in contrast to the spacer 100, thewalls 220,222 of the annular groove 202 are tapered toward one anotherwith the increasing depth of the groove 202, such that the floor 224 ofthe groove 202 is more narrow than the opening 226 of the groove.Further in this embodiment, the spacer 200 has a central bore 228.

[0077] Referring now to FIG. 2d, a set of intervertebral spacers 200 a-lof the invention are illustrated in a side view. Each spacer 200 a-l isformed generally similarly to the intervertebral spacer 200 of FIGS.2a-c, except that each spacer 200 a-l has a predetermined depth (denotedby the preferred dimension identified adjacent each spacer) provided inthat while each spacer 200 a-l shares the same annular groove dimensionsas the other spacers, each spacer 200 a-l has a different flangethickness dimension. For example, the flanges 2041,2061 are thicker thanthe flanges 204 a,206 a.

[0078] With regard to the instrument for the insertion and removal ofthe trial spacer elements, a first embodiment (particularly useful forinserting constant thickness trial spacers) of a spacer insertion toolincludes an elongated shaft and a handle at one end of the shaft. Thedistal end of the shaft includes semi-circular hook that is adapted tohold a trial spacer within an enclosure formed by the hook. The angleswept out by the hook is slightly greater than 180 degrees, but theinner diameter of the hook is only slightly larger than the centraltrunk of the trial spacer. Therefore, the trial spacer may be snappedinto the enclosure, but maintains complete rotational freedom within itsgrasp. A loading tool may be provided to assist in the loading andunloading of the trial spacer from the trial spacer insertion instrumentof this embodiment. This loading tool comprises a forked hook having twotines separated by a notch that engages the shaft of the insertion toolas the tines engage the flanges of the trial spacer, to force the trialspacer into the enclosure. Alternatively and/or additionally, the samedevice may be utilized to remove the spacer from the enclosure, byreversing the position of the forked hook relative to the insertion tooland the spacer.

[0079] Referring now to FIG. 5a, a first embodiment of a spacerinsertion tool 500 of the invention is illustrated in a side view. Theinsertion tool 500 includes an elongated shaft 502 and a handle 503 atone end of the shaft 502. At the other end of the shaft 502, theinsertion tool 500 includes a semi-circular hook 504 that is adapted tohold an intervertebral spacer of the invention within an enclosure 506of the hook 504. The central trunk of the spacer can be snapped into theenclosure 506 of the hook 504 so that the extent of the hook 504 fitsloosely within the annular groove of the spacer and is flanked by theflanges of the spacer. The central trunk of the spacer can also besnapped out of the enclosure 506.

[0080] In this regard, the hook 504 has an opening 508 that temporarilyexpands when the central trunk of the spacer is forced through theopening 508. That is, the outer diameter of the central trunk is greaterthan the width of the opening 508, so that the central trunk cannot passthrough the opening 508 without force. The application of a forcesufficient to cause the opening 508 to expand when confronted with thecentral trunk causes the central trunk to pass through the opening 508.After the central trunk has cleared the opening 508, the opening 508will contract. The temporary expansion in this embodiment is provided bythe hook 504 being formed of a material having a low elasticity and thehook 504 being provided with a stress notch 510 on the extent(preferably located opposite the opening 508 for maximum efficiency) toease the expansion.

[0081] Once the spacer is loaded into the enclosure, the opening 508,having contracted back to its resting width, prevents the central trunkfrom exiting the enclosure radially through the opening, because, asstated above, the outer diameter of the central trunk is greater thanthe width of the opening 508. Further, by flanking the extent of thehook 504, the flanges of the spacer prevent the spacer from exiting theenclosure laterally. The hook 504 therefore holds the spacer loosely inthe enclosure so that the spacer can rotate about the cylindrical axisof the central trunk while being held by the hook 504.

[0082] Referring now to FIG. 5b, a cutaway view of the insertion tool500 of FIG. 5a holding the spacer 100 of FIGS. 1a-c shows the extent ofthe hook 504 in cross-section and fitting within the annular groove ofthe spacer. It can be seen that to enable the spacer 100 to be looselyheld in the enclosure, the width of the extent is smaller than the widthof the annular groove, and the depth of the extent is less than thedepth of the annular groove if it is desirable for the flanges to fullyflank the extent. Preferably, as shown, the outer diameter of the hook504 is substantially equal to the outer diameter of the spacer 100.

[0083] Referring now to FIG. 6a-b, an embodiment of a loading accessory600 for a spacer insertion tool of the invention is illustrated in sideand top views, respectively. The loading accessory 600 can be used toease the passing of the central trunk of the spacer through the openingof the spacer insertion tool, both for loading the spacer into theenclosure and unloading the spacer from the enclosure. The loadingaccessory 600 includes an elongated shaft 602 and a forked hook 604 atan end of the shaft 602. A notch 606 having a base 608 separates thetines 610,612 of the forked hook 604.

[0084] The width of the notch 608 separating the tines 610,612 is wideenough to accommodate the width of the hook 504 of the insertion tool500 and the width of the shaft 502 of the insertion tool 500, but narrowenough so that the tines 610,612 can engage the edges of the flanges ofthe spacer. Preferably, as shown, the curvature of the tines 608,610follows the curvature of the edges of the flanges.

[0085] Referring now to FIG. 6c, the loading accessory 600 of FIGS. 6a-bis shown in operation to load the spacer 100 of FIG. 1a-c into thespacer insertion tool 500 of FIG. 5a. Initially, the spacer 100 ispositioned adjacent the opening 508 of the insertion tool 500. Then, thetines 610,612 of the loading accessory 600 are passed on either side ofthe shaft 502 of the insertion tool 500 such that the notch 606accommodates the shaft 502 and until the base 608 of the notch 606contacts the shaft 502. Then, the loading accessory 600 is rotated,using the contact between the shaft 502 and the base 608 as a fulcrum,to cause the tines 610,612 to engage the flanges 104,106 of the spacer100 and push them into the enclosure 506 of the tool 500. Applying aforce to the rotation, sufficient to cause the opening 508 of the tool500 to expand when confronted with the central trunk of the spacer,causes the central trunk to pass through the opening 508.

[0086] Referring now to FIG. 6d, the loading accessory 600 of FIGS. 6a-bis shown in operation to unload the spacer 100 of FIG. 1a-c from thespacer insertion tool 500 of FIG. 5a. Initially, with the spacer 100held by the tool 500, the tines 610,612 of the loading accessory 600 arepassed on either side of the shaft 502 of the insertion tool 500 suchthat the notch 606 accommodates the shaft 502 and until the base 608 ofthe notch 606 contacts the shaft 502. Then, the loading accessory 600 isrotated, using the contact between the shaft 502 and the base 608 as afulcrum, to cause the tines 610,612 to engage the flanges 104,106 of thespacer 100 and push them out of the enclosure 506 of the tool 500.Applying a force to the rotation, sufficient to cause the opening 508 ofthe tool 500 to expand when confronted with the central trunk of thespacer, causes the central trunk to pass through the opening 508. Thewidth of the notch 606 accommodates the width of the hook 504 as thespacer 100 is being pushed out of the enclosure 506.

[0087] The insertion tool of this first embodiment can be used to inserta series of constant thickness trial spacers (some of which may havebeveled flange edges for easing the insertion between the collapsedbones and into the space to be distracted). More specifically, thinnertrial spacers can initially be inserted into the spacer, followedsuccessively by thicker trial spacers until the desired spacing isachieved. Once the appropriate spacing has been achieved, immobilizationof the spine by fixation, fusion, or non-fusion techniques and devices,such as those set forth in co-pending U.S. patent application Ser. Nos.09/906,117 and 09/906,118, entitled “An Intervertebral Spacer DeviceHaving a Wave Washer Force Restoring Element” and “An IntervertebralSpacer Device Having a Spiral Wave Washer Force Restoring Element”,respectively, as well as U.S. Pat. No. 5,989,291, entitled “AnIntervertebral Spacer Device”, each of which has been assigned to thesame assignee as this present invention, the specifications of which areall fully incorporated herein by reference, may be desirable.

[0088] While simple distraction to a constant height across theintervertebral space is appropriate for standard disc compressionpathologies, in the case of scoliosis, simple constant thicknessdistraction is insufficient to remediate the pathological condition.What is necessary is the distraction of the sequence of spaces, each toan appropriate angle and height, such that the overall spinalconfiguration is anatomically correct. Tapered trial spacers, such asthose disclosed in the present application, are the first suchdistraction tools to provide such a tailored correction of themisangulation of the spinal bones.

[0089] More particularly, the surgeon inserts the tapered trial spacersinto the intervertebral space (presumably from the anterior, oranterio-lateral, approach) with the narrow edge of the trial spacerforming a wedge and sliding between the adjacent bones. By utilizingeither a second or third embodiment of the spacer insertion tool,described more fully hereinafter with respect to FIGS. 7a-c and 8 a-crespectively, the surgeon may turn the spacer around its axis within theintervertebral space to find the most appropriate rotational position(corresponding to the most desirable straightening effect on the spinalcolumn). Stated alternatively, each of the tapered trial spacers has anoverall wedge shape that generally corresponds to the pathologicaltapering of the adjacent bones that characterizes scoliosis. By rotatingthe wedge-shaped spacer after it has been placed between the adjacentbones, the overall disc alignment may be compensated, restoringappropriate anatomical status. It should be understood that additionalrotation of the spacer may restore lordosis to the spine, and thatover-rotation (if the particular spine is flexible enough) of the spacerwould result in a pathological curvature in the opposite direction.

[0090] Referring now to FIGS. 3a-c, a third embodiment of anintervertebral spacer 300 of the invention is illustrated in side, topand side cutaway views, respectively. Similarly to the spacer 100, thespacer 300 is a cylindrical disc with an annular groove 302 that forms acentral trunk 303 and radial flanges 304,306 at each end of the trunk303. However, in this embodiment, support portions 308,310 of the topand bottom surfaces 312,314 of the disc are not parallel, providing anoverall taper to the spacer 300 at an angle. Still, similarly to thespacer 100, the walls 320,322 of the annular groove 302 are parallel,such that the floor 324 of the groove 302 is as wide as the opening 326of the groove 302. Further in this embodiment, the spacer 300 has acentral bore 328.

[0091] Referring now to FIG. 3d, a set of tapered intervertebral spacers300 a-j of the invention are illustrated in a side view. Each spacer 300a-j is formed generally similarly to the intervertebral spacer 300 ofFIGS. 3a-c, except that each spacer 300 a-j has a predetermined maximumdepth (denoted by the preferred maximum depth dimension identifiedadjacent each spacer) and a predetermined minimum depth (denoted by thepreferred minimum depth dimension identified adjacent each spacer), eachprovided in that while each spacer 300 a-j shares the same annulargroove width dimension as the other spacers, each spacer 300 a-j has adifferent maximum flange thickness dimension and a different minimumflange thickness dimension. For example, the flanges 304 j,306 j have athicker maximum flange thickness dimension and a thicker minimum flangethickness dimension than the flanges 304 a,306 a.

[0092] Referring now to FIGS. 4a-c, a fourth embodiment of anintervertebral spacer 400 of the invention is illustrated in side, topand side cutaway views, respectively. Similarly to the spacer 200, thespacer 400 is a cylindrical disc with an annular groove 402 that forms acentral trunk 403 and radial flanges 404,406 at each end of the trunk403. However, in this embodiment, support portions 408,410 of the topand bottom surfaces 412,414 of the disc are not parallel. Still,similarly to the spacer 200, the flanges 404,406 are radially tapered inthat an outer edge 416 of the top surface 412 is tapered toward an outeredge 418 of the bottom surface 414. Further in this embodiment,similarly to the spacer 200, the walls 420,422 of the annular groove 402are tapered toward one another with the increasing depth of the groove402, such that the floor 424 of the groove 402 is more narrow than theopening 426 of the groove. Further in this embodiment, the spacer 400has a central bore 428.

[0093] Referring now to FIG. 4d, a set of tapered intervertebral spacers400 a-j of the invention are illustrated in a side view. Each spacer 400a-j is formed generally similarly to the intervertebral spacer 400 ofFIGS. 4a-c, except that each spacer 400 a-j has a predetermined maximumdepth (denoted by the preferred maximum depth dimension identifiedadjacent each spacer) and a predetermined minimum depth (denoted by thepreferred minimum depth dimension identified adjacent each spacer), eachprovided in that while each spacer 400 a-j shares the same annulargroove width dimension as the other spacers, each spacer 400 a-j has adifferent maximum flange thickness dimension and a different minimumflange thickness dimension. For example, the flanges 404 j,406 j have athicker maximum flange thickness dimension and a thicker minimum flangethickness dimension than the flanges 404 a,406 a.

[0094] It should understood that the various features of the differentembodiments of the intervertebral spacer of the invention discussedabove can be used in various combinations and permutations to form theillustrated embodiments and other embodiments of the intervertebralspacer of the invention. In some embodiments, the walls of the annulargroove are parallel. In other embodiments, they are not parallel. Insome embodiments where they are not parallel, they are tapered towardone another with the increasing depth of the groove. In otherembodiments where they are not parallel, they are tapered toward oneanother with the decreasing depth of the groove. In some embodiments,the support portions of the top and bottom surfaces are parallel. Inother embodiments, they are not parallel. In some embodiments, theflanges are radially tapered in that the outer edge of the top surfaceis tapered toward an outer edge of the bottom surface. In otherembodiments, the flanges are not radially tapered. In some embodiments,the spacer has a central bore. In other embodiments, the spacer does nothave a central bore.

[0095] It should be understood that while in the illustrated embodimentswhere spacers in a set have an overall taper, the angle of the overalltaper of each spacer in the set is the same as the angle of the overalltaper of the other spacers in the set, the invention encompasses a setof spacers in which the angle of the overall taper of each spacer in theset is different than the angle of the overall taper of at least oneother spacer in the set.

[0096] It should be understood that while in the illustrated embodimentswhere the spacer has an overall taper, the angle of the overall tapercan be predetermined, such that the maximum flange thickness and theminimum flange thickness can be selected to achieve a desired overalltaper angle.

[0097] It should be understood that while in the illustrated embodimentsthe spacers are shown as having a cylindrical shape, it should beunderstood that in other embodiment, the spacers can have oval, square,or rectangular cross-sections, or cross-sections of other shapes,provided that any corners are rounded as necessary to prevent damage tosurrounding tissue.

[0098] As suggested previously, the insertion, rotation and removal ofthe tapered trial intervertebral spacers requires an alternate spacerinsertion tool. This second embodiment of the spacer insertion toolincludes a handle and an elongated dual shaft, the dual shaftculminating in a trial spacer grasping pincer, rather than the simplehook of the first embodiment. This pincer differs from the hook of thefirst embodiment of the trial spacer insertion tool described above,inasmuch as the dual shaft includes a fixed shaft and a selectivelyengagable shaft which, together, form pincer. More specifically, thefixed shaft includes a semicircular hook portion of the pincer at itsdistal end, having an enclosure within which a trial spacer can beplaced. The selectively engagable shaft includes the complementaryportion of the pincer, which moves toward the hook portion to grasp andhold the trial spacer when the engagable shaft is engaged, and movesaway from the hook portion to release the trial spacer when theengagable shaft is disengaged. (The spacer can be unloaded and loadedwhen the engagable shaft is disengaged.) The engagement action preventsthe spacer from moving relative to the tool, and therefore permits thesurgeon to rotate the tapered spacer in between the vertebral bodies (bycontrast, the first embodiment of the trial spacer insertion instrumentpermitted the spacer to rotate freely in the enclosure of the hook).

[0099] Referring now to FIG. 7a, another embodiment of a spacerinsertion tool 700 of the invention is illustrated in a side view. Theinsertion tool 700 includes an elongated shaft 702 and a handle 704 atone end of the shaft 702. The insertion tool 700 further includes acompression assembly that is adapted to hold an intervertebral spacer ofthe invention at the other end of the shaft 702 so that the spacercannot move when held. The insertion tool 700 further includes a releaseassembly that is adapted to release the spacer from being held.

[0100] The compression assembly includes a semicircular hook 706 at theother end of the shaft 702 and a compression surface 708 adjacent thehook 706. The hook 706 has an enclosure 709 defined by the extent of thehook 706 and an opening 710 through which the central trunk can passfreely to be placed into the enclosure 709. That is, the width of theopening 710 is greater than the diameter of the central trunk. When thecentral trunk is placed within the enclosure 709, the extent of the hook706 fits loosely within the annular groove of the spacer.

[0101] The compression assembly further includes a compression trigger712 mechanically connected to the hook 706 such that as the compressiontrigger 712 is placed in an engaged position, the hook 706 is pulledtoward the compression surface 708. The mechanical connection includes arod 714 connected at one end to the hook 706 and at the other end to aplate 716. A rod 718 protruding from the plate 716 is engaged by a slot720 in a lever 722 attached to the compression trigger 712. When thecompression trigger 712 is engaged, the rod 714 of the lever 722 pullsthe plate 716 by the slot 720. The plate 716 in turn pulls the rod 714,which in turn pulls the hook 704 toward the compression surface 708.

[0102] When the hook 706 is pulled toward the compression surface 708when the central trunk of the spacer is in the enclosure 709, thecentral trunk is compressed within the enclosure 709 between the hook706 and the compression surface 708 so that the spacer cannot move.

[0103] The release assembly includes a spring 724 biasing thecompression trigger 712 to a disengaged position. Therefore, after thecompression trigger 712 is released, it moves to the disengagedposition. However, so that the central trunk remains compressed withinthe enclosure even after the compression trigger 712 is released (e.g.,so that the surgeon does not need to continue holding the compressiontrigger 712 to effect the compression), the compression assembly furtherincludes teeth 726 on the rod 714 and corresponding teeth 730 thatconfront the rod teeth 726 to prevent the rod 714 from retreating, tomaintain the compression.

[0104] The release assembly further includes a release trigger 732 thatcan be engaged to release the rod teeth 726 from the corresponding teeth730 to allow the rod 714 to return to its rest position, therebyalleviating the compression. More specifically, the release trigger 732has the corresponding teeth 730 and the release assembly furtherincludes a spring 734 that biases the release trigger 732 toward aposition in which the corresponding teeth 730 engage the rod teeth 726.This arrangement allows the release trigger 732 to be engaged bypressing the release trigger 732 with a force great enough to overcomethe bias of the spring 734, so that the corresponding teeth 730 aredisengaged from the rod teeth 726. Therefore, when the release trigger732 is pressed, the compression is alleviated, and the central trunk ofthe spacer can be freely passed through the opening 710 to be taken outof the enclosure 709.

[0105] Referring now to FIG. 7b, a cutaway view of the insertion tool700 of FIG. 7a holding the spacer 400 of FIGS. 4a-c shows the extent ofthe hook 706 in cross-section and fitting within the annular groove ofthe spacer as the spacer is compressed between the compression surface708 and the hook 706. It can be seen that the width of the extent of thehook 706 is smaller than the width of the annular groove, and the depthof the extent is less than the depth of the annular groove if it isdesirable for the flanges to fully flank the extent. Preferably, asshown, the outer diameter of the hook 706 is substantially equal to theouter diameter of the spacer 400.

[0106] Referring now to FIGS. 8a-b, yet another embodiment of a spacerinsertion tool 800 of the invention is illustrated in open and closedside views, respectively. The insertion tool 800 includes an elongatedshaft 802 and a handle 804 at one end of the shaft 802. The insertiontool 800 further includes a compression assembly that is adapted to holdan intervertebral spacer of the invention at the other end of the shaft802 so that the spacer cannot move when held. The insertion tool 800further includes a release assembly that is adapted to release thespacer from being held.

[0107] The compression assembly includes a claw 806 at the other end ofthe shaft 802 having opposing pincers 807 a, 807 b, each providing oneof opposing compression surfaces 808 a, 808 b. The claw 806 has anenclosure 809 defined by the extents of the pincers 807 a, 807 b and anopening 810 through which the central trunk can pass freely to be placedinto the enclosure 809 when the claw 806 is open (i.e., when theopposing pincers 807 a, 807 b are separated). That is, the width of theopening 810 is greater than the diameter of the central trunk when theclaw 806 is open. When the central trunk is placed within the enclosure809, the extents of the pincers 807 a, 807 b fit loosely within theannular groove of the spacer.

[0108] The compression assembly further includes a compression slide 812that when moved to an engaged position (here, a forward position shownin FIG. 8b) closes the claw 806. The closure of the claw 806 by thecompression slide 812 is effected as follows. One of the pincers 807 ais in a fixed position relative to the elongated shaft 802 whereas theother pincer 807 b is adapted to rotate about an axis transverse to theshaft 802. In this embodiment, the rotation is provided by a pin 813passing through each pincer at a rotation point along the transverseaxis. One position of the movable pincer 807 b along the rotation path(shown in FIG. 8a) defines the opened claw 806 in that the pincers 807a, 807 b are separated. Another position of the movable pincer 807 balong the rotation path (shown in FIG. 8b) defines the closed claw 806in that the pincers 807 a, 807 b are brought together. When the pincers807 a, 807 b are separated, an engagement surface 814 of the movablepincer 807 b is placed in an available compression path of an engagementsurface 816 of the compression slide 812. The engagement surface 814 istapered so that when the compression slide 812 is moved to the engaged,the engagement surface 816 of the compression slide 812 moves along theavailable compression path and engages the tapered surface 814 to pushthe surface 814 aside and thereby cause a rotation of the movable pincer807 b to the position defining the closed claw 806.

[0109] When the pincers 807 a, 807 b are thereby brought together toclose the claw 806 when the central trunk of the spacer is in theenclosure 809, the compression surfaces 808 a, 808 b come to bear on thecentral trunk to compress it within the enclosure 809 so that the spacercannot move.

[0110] The release assembly includes a spring 818 biasing the movablepincer 807 b to the rotation path position defining the open claw 806.Therefore, when the compression slide 812 is moved to a disengagedposition (here, a backward position), the engagement surface 816 of thecompression slide 812 moves along an available release path (here, abacktracking along the compression path) and frees the engagementsurface 814 of the movable pincer 807 b to allow the engagement surface814 to return to a place in the available compression path by thebiasing action of the spring 818. When the claw 806 is open, thecompression is alleviated and the central trunk of the spacer can befreely passed through the opening 810 to be taken out of the enclosure809.

[0111] The release assembly further includes at least one barrier 820 a,820 b that limits the biasing action of the spring 818 by preventing themovable pincer 807 b from rotating beyond the position that places theengagement surface 814 in the available compression path. In thisembodiment, confrontation surfaces 822 a, 822 b on the movable pincer807 b confront the barriers 820 a, 820 b as the pincer 807 b rotatestoward the rotation path position defining the open claw 806 under thebiasing force of the spring 818. When the engagement surface 814 isreturned to the place in the available compression path, the barriers820 a, 820 b prevent the confrontation surfaces 822 a, 822 b fromadvancing further. The spring 818 and the barriers 820 a, 820 b maintainthe movable pincer 807 b in this position until the compression slide812 is advanced toward the engaged position by a force great enough toovercome the biasing force of the spring 818.

[0112] Referring now to FIG. 8c, a cutaway view of the insertion tool800 of FIGS. 8a-b holding the spacer 400 of FIGS. 4a-c shows the extentsof the pincers 807 a, 807 b in cross-section and fitting within theannular groove of the spacer as the spacer is compressed between thecompression surfaces 808 a, 808 b. It can be seen that the width of eachextent is smaller than the width of the annular groove, and the depth ofeach extent is less than the depth of the annular groove if it isdesirable for the flanges to fully flank the extents. Preferably, asshown, the outer diameter of the claw 806 is substantially equal to theouter diameter of the spacer 400.

[0113] There are alternative insertion and rotating instruments that maybe designed, so long as they selectively and alternatingly release orhold the trial spacer securely against rotation (the spacer can't rotatefreely if it is to be turned in the intervertebral space). The taperedtrial spacers themselves can include angle markers that clearly indicateto the surgeon the amount of rotation that was necessary for thecorrection of the spinal deformity. Such angle markers can also serve asa guide for the implantation of a secondary bone graft (e.g., a femoralring) or another intervertebral spacer device.

[0114] Once the surgeon has determined the appropriate geometry for thesurgical implants via the trial spacers, he or she is ready toimmobilize the spine in that position. While multiple ways forimmobilizing the spine are disclosed in the prior art, any one of whichmay be suitable for the specific surgical patient's treatment, threealternative ways are herein described.

[0115] First, the trial spacers may be left in the patient while rodfixation apparatuses (anterior or posterior) are mounted to the spine,thereby holding the spine in its desired orientation even after thetrial spacers are subsequently removed. Alternatively, surface platingand/or intervertebral cage devices may be mounted to the spine topromote fusion without the need for bulky rod assemblies. (While thisapproach may seem more surgically desirable, questions regarding thelong-term stability of these constructs have led to some surgeons tochoose combinations of rodding and cages.)

[0116] A third approach to immobilizing the corrected spine is to inserta shaped bone graft, or suitably contoured porous metal spacer, into theproperly distracted intervertebral space, and either plating or usingrod fixation to hold the construct stable as the spine fuses. Theinsertion of a femoral ring allograft, or porous metal implant, into anintervertebral space is described more fully in co-pending U.S. patentapplication Ser. No. 09/844,904, entitled “A Porous Interbody FusionDevice Having Integrated Polyaxial Locking Interference Screws”,assigned to the same assignee as the present invention, thespecification of same being incorporated herein by reference.

[0117] The tapered trial spacers may also serve as precursors (measuringinstruments) for another spacer (e.g., a porous metal spacer), similarlyshaped, which is inserted into the intervertebral space by the sameinstrument.

What is claimed is:
 1. An intervertebral space distraction andimplantable device assembly comprising: a plurality of sequentiallyaxially wider disc spacer elements, the sequential insertion and removalof which, into an intervertebral space effects a widening of theintervertebral space, such that a desired anatomical spacing of adjacentvertebral bones may be restored, said plurality of sequentially axiallywider disc spacer elements including at least one porous spacer elementhaving a width equivalent to the width of the spacer element thatrestores the desired anatomical spacing.
 2. The intervertebral spacedistraction assembly as set forth in claim 1, wherein said disc spacerelements each include beveled upper and lower circumferential radialedges which facilitate the application of the desired spreading force tothe adjacent vertebral bones.
 3. The intervertebral space distractionassembly as set forth in claim 1, wherein said disc spacer elements eachinclude an engagement locus which couples with a corresponding insertionand removal tool to facilitate the same.
 4. The intervertebral spacedistraction assembly as set forth in claim 3, wherein said engagementlocus comprises an axially medial groove into which said insertion andremoval tool can be seated.
 5. The intervertebral space distractionassembly as set forth in claim 4, wherein said axially medial groovecomprises a constant width, such that each disc spacer element mayrotate freely within the corresponding insertion and removal tool. 6.The intervertebral space distraction assembly as set forth in claim 4,wherein said axially medial groove comprises a radially widening groove,such that each disc spacer element may be prevented from rotating freelywith respect to the corresponding insertion and removal tool by aclamping action thereof, thereby permitting the controlled rotation ofthe corresponding disc spacer element within the intervertebral space bymanipulation of the insertion and removal tool.
 7. The intervertebralspace distraction assembly as set forth in claim 1, wherein said discspacer elements each further comprise diametrically tapered upper andlower surfaces.
 8. The intervertebral space distraction assembly as setforth in claim 7, wherein each of said disc spacer elements furtherincludes at least two relative angle designation marks on at least oneof said upper and lower surfaces such that a surgeon user may readilyvisually determine the rotational angle of said disc spacer elementrelative to a known reference.
 9. The intervertebral space distractionassembly as set forth in claim 7, wherein said disc spacer elements eachinclude beveled upper and lower circumferential radial edges whichfacilitate the application of the desired spreading force to theadjacent vertebral bones.
 10. The intervertebral space distractionassembly as set forth in claim 7, wherein said disc spacer elements eachinclude an engagement locus which couples with a corresponding insertionand removal tool to facilitate the same.
 11. The intervertebral spacedistraction assembly as set forth in claim 10, wherein said engagementlocus comprises an axially medial groove into which said insertion andremoval tool can be seated.
 12. The intervertebral space distractionassembly as set forth in claim 11, wherein said axially medial groovecomprises a radially widening groove, such that each disc spacer elementmay be prevented from rotating freely with respect to the correspondinginsertion and removal tool by a clamping action thereof, therebypermitting the controlled rotation of the corresponding disc spacerelement within the intervertebral space by manipulation of the insertionand removal tool.
 13. An intervertebral spacer implantable element set,comprising a plurality of intervertebral spacer implants, each implanthaving non-parallel upper and lower surfaces providing a diametricaltaper to the implant, the diametrical taper having a taper angle, thetaper angles being selected to counter a misalignment angle of a spacebetween adjacent vertebral bones in a scoliotic patient.
 14. The set ofclaim 13, wherein at least one of the implants comprises at least one ofbone and porous metal.
 15. The set of claim 13, wherein each implantincludes an annular groove.
 16. The set of claim 13, wherein eachimplant has a different taper angle from each other implant.
 17. The setof claim 10, wherein each implant has a different axial thickness fromeach other implant, the axial thicknesses of the set being selected toincrease from one implant to another.
 18. The set of claim 16, whereineach implant has a different taper angle, the taper angles of the setbeing selected to increase by an angular increment from one implant toanother.